The present invention relates to a driving direction changing apparatus of a rear hub for a bicycle, and more particularly, to a driving direction changing apparatus of a rear hub for a bicycle, having a driving portion and a driving direction changing portion, which is capable of always outputting driving force in only one direction, that is, forward, by receiving the forward and rearward driving force of a pedal shaft.
In general, a bicycle can travel in only one direction, that is, travel forward by pedaling forward, thereby easily causing fatigue in rider""s leg and uneven development in a leg muscle when the rider bicycles for many hours.
Thus, in order to solve the problems, many inventors have made an effort in the development of a bi-directional pedaling apparatus which can be applied to a conventional one-directional pedaling bicycle.
The bi-directional pedaling apparatus developed until now may be classified into three fields roughly according to the methods adopted therefor. That is, there are methods using an auxiliary gear, a bevel gear and a planetary gear.
As a representative invention related to the bi-directional pedaling apparatus, Manrzoursos et al. (EPO Publication No. 0,369,925) discloses a bi-directional pedaling apparatus adopting the auxiliary gear, Foster (U.S. Pat. No. 5,435,583) discloses a bi-directional pedaling apparatus adopting the bevel gear and a clutch, and the present applicant (Korean Patent Application No. 95-47910) discloses a bi-directional pedaling apparatus adopting the planetary gear.
However, because the above bi-directional pedaling apparatuses must be attached to the outside of the pedal shaft, the attached apparatus is protruded toward the outside of a bicycle frame, thereby obstructing the pedaling by a rider. In addition, due to the protruded portion, it is difficult to attach the bi-directional pedaling apparatus to a newly developed bicycle which can be folded for portability.
Thus, the above problems has raised requirements in development of a transmission for a bicycle, which can allow the bi-directional pedaling apparatus to be attached to a shaft of a rear wheel.
In order to reduce fatigue in legs during pedaling and effectively utilize the energy applied to the pedals, pedaling rhythm and pedaling force applied to the pedals should be constant. The transmission for a bicycle is developed for satisfying the above conditions, which controls a gear ratio between a driving sprocket and a driven sprocket, thereby properly applying the pedaling force according to a driving resistance to the driving of the bicycle.
As the transmission, there are an external type and an internal type. The external transmission directly changes the gear ratio while applying a chain on a plurality of sprockets having different diameters in sequence which are installed at a pedal shaft and a hub shaft, and the internal transmission changes the gear ratios by installing planetary gears in the rear hub shell.
The internal transmission can be much miniaturized compared with the external transmission and protected from external impact while blocking the influx of dust or foreign substance since the internal transmission is installed in the hub shell.
Due to these advantages, Korean Patent Application No. 97-25869, applied by the present inventor, may be referred to as an example of the inventions related to the internal transmission.
The apparatus of the above invention comprises a driving portion, a driving direction changing portion capable of changing the rearward driving force of the driving portion into the forward direction and a transmission portion capable of reducing the forward rotation rate of the driving direction portion and idling the rear wheel. The driving portion includes a driven sprocket housing with a cylindrical shape, which is rotatably installed at a hub shaft of the rear wheel and elastically supported along the circumference by forward and rearward direction pawls arranged with a predetermined interval, a ratchet fixing ring of the hub shell, coupled with the forward direction pawl of the driven sprocket housing, and a ratchet ring coupled with the rearward direction pawl of the driven sprocket housing. The driving direction changing portion includes a first carrier having planetary gears capable of rolling against the hub shaft while being coupled with the ratchet ring, a first sun gear capable of rolling against the planetary gears of the first carrier, a second carrier fixed to the hub shaft such that the first sun gear and the planetary gears can do the rolling movement, and a second sun gear capable of rolling against the planetary gears of the second carrier and having a forward direction pawl elastically protruded from the circumference for the forward driving. Also, the transmission portion includes a third sun gear capable of connecting with the forward direction pawl of the second sun gear and the fixing ratchet fixed to the hub shell, a third carrier capable of rolling against a gear integrally formed in the hub shaft, the third sun gear and the planetary gears, and a clutch slidably attached between the third carrier and the inner diameter of the second sun gear to be elastically and slidably movable by a level installed outside.
That is, according to the above invention, the driven sprocket housing having the forward and rearward direction pawls is attached in the hub shell, so that the driving direction changing portion rotates the ratchet fixing ring fixed to the hub shell according to the driving direction of the driven sprocket. For example, if the driven sprocket drives forward, the forward direction pawl of the driven sprocket housing rotates the ratchet fixing ring forward, thereby outputting the forward driving force to the hub shell.
Also, the driving portion and the transmission portion which operates in connection with a carrier means are arranged in parallel. Thus, if the rearward driving force is provided, the rearward direction pawl of the driven sprocket housing drives the carrier means, thereby transferring the driving force to the transmission portion connected with the carrier means.
Particularly, the transmission portion can change the rearward driving force of the driving portion into the forward driving force by changing the position of the clutch whose operation is controlled from the outside, and simultaneously maintain or reduce the driving rate, and change the rearward driving force into idling.
However, because the transmission portion and the pawls and the ratchets of the driving portion are always engaged in the above invention, the gears may be damaged by overload during the forward and rearward driving, or noise by the engagement may be generated, requiring a large gap.
It is an object of the present invention to provide a driving direction changing apparatus of a rear hub for a bicycle, having a driving portion and a driving direction changing portion, which is capable of always outputting driving force in only one direction, that is, forward, by receiving the forward and rearward driving force of a pedal shaft.
According to an aspect of the above object, there is provided a driving direction changing apparatus of a rear hub of a bicycle in which a transmission device using planetary gears is installed, the apparatus comprising: a driving portion including a driven sprocket housing movably connected to a hub shaft, a plurality of first and second clutch groups installed at the outer circumference of the leading end of the driven sprocket housing, a first carrier for supporting the first and second clutch pin groups, a clutch housing for driving a hub shell by the expansion force caused by the frictional force of the first clutch pin group, and a first separation preventing member for preventing the clutch housing from being separated; a driving direction changing portion including a first ring gear for driving the hub shell by the expansion force caused by the frictional force of the second clutch pin group, a first idle gear rotating being engaged with a gear formed at the inside of the leading end of the first ring gear, centering a rotating shaft, a second idle gear rotating being engaged with the first idle gear, centering a rotating shaft, a second carrier for supporting the first and second idle gears, and a second ring gear having an inner gear engaged with the second idle gear; and a multi-stage transmission portion connected to one end of the driving direction changing portion and integrally formed with a second separation preventing member installed at the outer circumference.
According to another aspect of the above object, there is provided a driving direction changing apparatus of a rear hub of a bicycle, the apparatus comprising: a driving portion including a driven sprocket housing movably connected to a hub shaft, an idle gear rotating being engaged with a gear formed at the leading end of the driven sprocket housing, and a carrier rotatably supporting the idle gear centering a rotating shaft; and a driving direction changing portion installed inside and outside the carrier, for changing the driving of the driving portion into the forward and rearward directions.
Thus, in the driving direction changing apparatus according to the present invention, the driving direction changing portion for capable of driving the bicycle forward while pedaling counterclockwise is installed, such that the forward traveling by the forward and rearward pedaling can be controlled according to the rider""s intention, thereby optimizing efficiency in traveling and uniformly developing legs"" muscle while reducing fatigue.
According to the basic structure of the driving direction changing apparatus of the present invention, the hub shell is rotatably installed on the hub shaft by bearings, having an xe2x80x9cHxe2x80x9d-shaped cross-section, and the driving direction changing portion and the driving portion are installed at the sides thereof. Also, the driven sprocket housing fixed to the driven sprocket which drives in connection with the pedal shaft via a chain is tightly installed at the side of the hub shell.
Also, a conventional multi-stage transmission portion is installed in the hub shell to operate in connection with the driving direction changing portion and the driving portion.
The driving force transfer mechanism in the present invention is as follows briefly.
First, the driving force generated by pedaling reaches the driven sprocket via a crank, a driving sprocket and a chain in sequence. The driving force is transferred to the driving portion and the driving direction changing portion of the apparatus of the present invention in sequence while the driven sprocket rotates together with a driving wheel.
The driving force transferred to the driving direction changing portion is transferred to the transmission portion, and the transmission force of the transmission portion is then output to the hub shell, thereby driving the rear wheel of the bicycle.